Pneumatic cabin temperature control system



United States Patent PNEUMATIC CABINTEMPERATURE coNTRoL SYSTEM TorstenH, Lindbom, Garden City, N. Y., assignor to Fairchild Engine and-Airplane Corporation, Hagerstown, Md., a corporation of MarylandApplication January 27, 1956,1serialNo; 561,821` 8 Claims.` (01.1236-1)The present invention relatesft temperaturecontrol` sion turbine, andanother part through a valve controlled The'temperature control is theneffected the iluid iliow in the by-pass channel luy-,pass channel.` by:the `control of and "in the channelincluding the cooling unit, so that aproper mixture of hot and cooled air can be combined and fed to theenclosure.`

In accordance with the invention, theautomatic control of the by-pass`valve"controlling the flow of air through the by-,pass `channel inasystem of the aboveitype, is

eectuated in air within the response to lboth the temperature of the`enclosure and-the rate of changeof the temperature ofthe air mixturebeing fed to the enclosure;`

More particularly, the by-pass channel valve is automatically controlledby a Wheatstone bridgetype of balancing apparatus differentiallyresponsive-to pressureisignals developed bya temperature sensor and arate of change of temperature sensor. The automatic balancing device inturn controls a positional servomechanism operating the byjpass valve.

For a more completeunderstanding of the invention reference maybe had tothe following `detailed description taken in conjunction with' thesingleigure of the drawing which `is partly in the form of a schematicdia" grain, and partlly a sideelevation in vertical cross-sectionoflan'exemplary embodiment of the system, in accordance with theinvention.

In tliepreferred embodiment, a ilnid such as air `is fed under pressurefrom a suitableuid pressure source (not shown.) through a condit 10includinga cooling unit 12 leading to an enclosurell, suchas an aircraftcabin: A

fbypas's channel, including aninput chamber 13 connected to a pointinthe conduit 10`upstrea1n of the cooling unit 12, a valve seat 14,` anoutput chamgerlS, and a bypass conduit ltf connected'between the outputchamber `15 and a point in the conduit A10 downstream of the coolingunit 12, bridges the cooling unit 12."

Flow through thby-pass channel is controlled by al by-passvalveot thepoppet type, `including a valv'e head 18"adap`t`ed 'to rest on the valveseat 14,A and a valve pintle 19; Theupper `portion of the pintle y19 isfixedly `connected t `a diaphragm backing plate 20"o`f a flexible da#phra'gm` 21. The flexible` diaphrag`m"21" separates the valveoutputchamber" 1S and a valve operating chamber 22,` and is `of ataperedtiv'e" area which varies design suitable to provide an effec` inaccordance with the axial posi tion ofthe-diaphragm; The chambers'and`22lare '2,870,964 latented Jan.=27-,i'1959 sealc'd from each otherwith the execeptionof a passage` way 23, passingaxially` through theupper portion ofthe pintle 19` an'd leading fronrthe operating chamber22 throughan orifice` 24 tothe valve output chamber 15,- and servingftobleed the operating chamber 22;

The operating chamber 2:2 is connected'tola point in the conduit 10upstream of both the cooling `unit=12A and the Valve input chamber 13 bymeans ofaleadconduit 26,A a 4branch conduit 27 and a fixed restriction28.2

Positioned above the` valve operatingchamber 22 a diaphragm`wpa-differential pressuresignal sensing means includes a chamber 30connected by a -conduit 31 tol a temperature sensor 32,` located in theenclosure in which the temperature is being controlled, and also througha fixed restriction" 33 communicating with `the conduit 31; a branchconduit `34 and thelead conduit 26 to the point inL the conduit 10`upstream of the `by-pass valve input chamber `13 and i the cooling unit12.` The differentiall pressure'signal sensingmeans also `includesachamber 40 connectedgby a conduit 41to the rate sensor 42, and alsothrough a fixed restriction- 43 communicatingwith lthe con` duit 41, anda Ibranch conduit 44 to the leadconduit 26." Thechamberslluand40"areseparated from each other by means ofaflexiblediaphragm 45.A

The lower chamber 30 is separated from the valve operi ati'ngchamber bymeans of a flexible diaphragm 46,

while the upper chamber 4t? is separated from a `chamber 47 by means ofa flexiblediaphragm 48, The chamber 47 is connected through a tubularmember 49 having an opening 50 to the valve' operating chamber 22permitting,v the free llow of fluid therebetween, .thereby maintainingthe pressure on the upperside of the diaphragm `48V equal tolthepressure on the lower side of the diaphragm 446;` The tubular member 49is tiXedly attached tota back plate 51 of the `diaphragm 48, a back 4S,and the back plate 53 of the diaphragm 46, so that its movementisdirectly Acontrolled by the pressures actingf upon these threediaphragms and the resulting -forces` created thereby. p

The tubular mem'ber 49 is positioned axially of and above the pin'tle 19ofthe by-pass valve, and thek lower-` most portion 54 of the tubularmember 19 is positioned just above the orice 24 at the top of the pintle19 and is movable relative thereto, forming a means to control theeifective area of the orifice 24.

The ellective areas A46 and A48 ofthe iiexible dia` phragrns 46 and 48are equal. Since the valve operating chamber 22 is in free communicationwith the chamber 47 through the tubular member 49 and the opening 50,

so that `the pressures in the two chambers are equal, iti

is evident that the downward force on the flexible diaphragm 48 is equaland opposite to the upwardforce on the diaphragm 46, thereby making thediaphragm assembly formed by `the diaphragms `45, 46 and 48 inde;pendent of the surrounding pressure.

The temperature sensor 32 is of the bellows type and acts in aconventionalmanner to control the effective area of a bleed orifice 60ina conduit 31, in response to the temperature of the surroundingrnediuminwhich it is located, via., theair inside the cabin 11. The `temperaturesensor 32is adjusteds'o that the effective areaof'tle' bleed orifice 60has a predetermined Value or set point for a` predeterminedtemperature'of the air within the cabinll.

The `rate sensor in` thelA applicants'` copnding" application SerialANo.` 561,490, filed January 26, 1956, for Temperature 'Sens` ing`Device, and comprises a thin metal strip 65 and ablock 66, ofsubstantially equal lengths, and composed of the same material such `asaluminum. A lever means the block 66 and has one en'lnc-I tact with thethi'ninetalistrip `65,` the other'en'd'actg" 67 is pivoted1 on plate 52of the diaphragm` 42 is preferably of a type disclosed conduit 41. Asdescribed more fully in the applicants above-mentioned copendingapplication Serial No. 561,490, for any given temperature, the relativeposition of the lever means 67 andthe orifice 68 will be such as toprovide a constant predetermined effective bleed areafor the orice 68.However, since the thin metal strip 65 will react to changes oftemperature more rapidly than the block 66, when the temperature of thefluid in which the rate sensor 42 is immersed varies, the effective areaof the orifice 68 is varied as a function of the rate of change oftemperature of the fluid in the conduit 10. More particularly, in theembodiment shown, when the temperature of the iiuid in the conduit 10increases, the thin metal strip 65 expands more rapidly than the block66 and the effective area of the orifice 68 is increased. Similarly, asthe temperature of the fluid in the conduit 10 decreases, the thin metalstrip 65 contacts more rapidly than the block'66 and the effective areaof the bleed orifice 68 is decreased. However, as soon as thetemperature of the fluid in the lconduit 10 stabilizes, the effectivearea of the orifice 68 returns to its normal size. Thus the rate sensoris sensitive to changes in temperature, but is independent of thestabilized temperature of the fluid inthe conduit 10.

In thepreferred embodiment, the rate sensor 42 is positioned in theconduit 10 suiciently upstream of the cabin 11 to give a rapid responseto the change in temperature of the fluid being pumped through theconduit 10 into the cabin.

In order to obtain equilibrium of the diaphragm assembly, the electivearea of the orifice 60 of the temperature sensor must be in a xedproportion to the effective area of the orifice 68 of the rate sensor,as will be shown hereinafter, and the pressures in the conduits 31 and41 and the chambers 30 and 40 must be equal.

In considering the operation of the system, it is first assumed thatIthe temperature of the air within the cabin 11 is at the desired value,so that the effective area of the bleed `orifice 60 of the temperaturesensor 32 is at its set point. Further, it is assumed that thetemperature of the uid passing through the conduit 10 is constant sothat the rate sensor 42 is at its set point. Under those conditions, thepressures in the chambers 30 and 40 are equal.

Assuming ow through the by-pass channel, the cooling unit andthe controlconduits to be sonic, the pressure P30 in the chamber 30 is determinedby the following relation:

Peor-:Paa-

where P20 is the pressure in the conduit 26 and the upstream supplypressure of the conduit 10, A33 is the area of the fixed restriction 33,and A is the effective area of the bleed orifice 60 in the temperaturesensor. Under the same conditions of flow, the pressure P00 in thechamber 40 is determined by the following relation:

Aas

where A03 is the elective area of the fixed restrictionY 4 I Thepressure P22 in the valve operating chamber 22 is determined by thefollowing ratio:

where A24 is the effective area of the orifice 24 leading from the valveoperating chamber 22 and A20 is the effective area `of the fixedrestriction 28 leading from the branch conduit 2,7 into the valveoperating chamber 22.

ln the equilibrium state, where the pressures P30 and P00 are equal, theposition of the control means formed by the lower end 54 of the tubularmeans 49 is set. Further, under equilibrium conditions, the pressure inthe valve operating chamber 22 will be sufficient to balance the forcesacting upon the valve head 18. This pressure is a function of theeffective area A20 of the orifice 24 leading from the valve operatingchamber 22 to the output chamber 15. Thus the elective area A20 of theorifice 24, under the particular equilibrium conditions, is at aconstant value.

The system automatically controls the cabin temperature in the followingmanner: When the air in the cabin 11 is heated, for example, by sunlightcoming through the cabin window, the cabin temperature rises and theeffective area A00 of the bleed orifice 60 is decreased. From aninspection of Relation 1, it is seen that such a decrease will cause anincrease in the pressure P30 in the chamber 30. This increase in thepressure P30 disturbs the equilibrium of the diaphragm assembly 45, 46,48 and produces a resultant upward force moving the control means 54away from the orifice 24, thereby increasing the effective area A20. Asshown by Relation 4, the increase in the effective area A34 causes adecrease in the pressure P22 in the valve operating chamber 22. When thepressure P22 decreases, a resultant upward force is created on theflexible diaphragm 0 21 and the valve head 18 of the by-pass valve movesupwardly acting to restrict the passage of warm air through the by-passchannel 16. Thus the temperature of the air fed from the conduit 10 intothe cabin 11 is decreased.

The air mixture in the conduit 10 is then varied until the cabintemperature returns to and stabilizes at the predetermined desired valueand the effective area A00 of the orifice 60 in the temperature sensor32 is returned to its set point. At that time, the valve head 18 and thediaphragm 21 are in a new stabilized position. Thus it. is seen that thetemperature sensor performs a `reset as well as a temperature sensingfunction.

Alternatively, it is assumed that the cabin temperature drops, producingan increase in the effective area A00 of the temperature sensor orifice60. This increase in the effective area A00 is accompanied by a decreasein the pressure P00 and a downward movement of the control means 54occasioning a corresponding decrease in the effective area A20. When theeffective area A20 decreases,

i the control pressure P22 in the valve operating chamber 22 duit 16.The diaphragm assembly 45, 46, 48 will then be restored to itsequilibrium condition when the cabin teinperature returns to thepredetermined temperature.

Now it is assumed that a change in the supply temperature occurs,causedby, for example, an acceleration of a jet engine of the aircraftwith which the system is associated. If the change is in effect anincrease in the temperature of the air owing through the conduit 10, theeffective area A00 of the bleed orifice 68 of the rate sensor increases.As seen from Relation 2, when the eiective area A00 increases, thepressure P00 decreasesproducing a resultant upward force on thediaphragm assembly 45,

46, 48 anda corresponding movementof the controlA means 54 away fromtheorifce 24, thereby enlarging the eective areaA24 and reducing thecontrol pressure P22. When this occurs, the valve head 18 moves upwardlyso as to restrict the owof `warm airthrough the by-pass conduit.16.`Alternatively, if the supply temperature starts to drop, `the eiectivearea A68 of thebleed orifice ofthe rate sensor decreases, therebyincreasing` the pressure,n P40, causing, a resultant downward force onthe diaphragm assemblyl45, 46, 48 and a decreasein. the elfectiveareaA`24. Whenthis, occurs, the control pressurePzg increasesand thevalve head 1S moves downwardly permitting a greater flow of warm airthrough the by-pass channel 16.

. The proportion of the effective areas .of` the fxed restriction .28.`and the variable orifice 24, in the preferred embodiment offtheinvention, is such that the positional servomechanism controlled therebyis very stiff.` Thus a very small change in effective area A24 of thevariable orifice 24 produces a relatively large change in pressure P22.Further, in the preferred embodiment, the stroke of the valve pintle 19and the valve head 18 is` kept very small, so that the effective inertiais very small.

Thus there has been provided a novel and` improved automatic temperaturecontrol system wherein the temperature of an enclosure is maintained ata predetermined level by automatically controlling the temperature ofthe fluid supplied to the enclosure, in response to variations in theenclosure temperature and in the rate of change of the supplytemperature.

The above embodiment is meant to be merely exemplary, and it will beobvious to those skilled in the art that it is susceptible ofmodification and variation without departing from the spirit and scopeof the invention. For example, While the system has been described withrelation to the temperature control of air in an aircraft, it will beobvious that the principles of the invention willbe equally applicableboth to other types of enclosures and to other compressible fluids.Also, while specific embodiments of temperature sensors and rate ofchange of temperature sensors have been disclosed, it Will be evidentthat other forms of suitable sensing devices adapted to perform similarfunctions can be substituted therefor. Accordingly, the invention is notdeemed to be limited except as defined by the appended claims.

I claim:

l. An automatic temperature control system for an en-` closure fed froma fluid pressure source by a conduit having a cooling means therein, aby-pass channel for passing fluid around said cooling means, and a valvefor con-` trolling the flow of iluid through said by-pass channel,comprising a positional servomechanism for operating said valve, meansfor sensing the temperature in said enclosure to provide a variablecontinuous signal representative thereof, means for sensing the rate ofchange of temperature of the fluid in said conduit to provide a variablecontinuous signal proportionate thereto, and differential meansresponsive to said temperature sensing signal and said rate of change oftemperature sensing` signal for controlling the operation of saidservomechanism.

2. An automatic temperature control system for an enclosure fed from afluid pressure source by a conduit having a cooling means therein, aby-pass channel for passing fluid around said cooling means, and a valvecontrolling the flow of iluid through said by-pass channel, comprising apositional servomechanism for operating said valve, a differentialpressure signal responsive actuating means for controlling the operationof said positional servomechpositional anism, means responsive to thetemperature in said en-` closure for providing a rst pressure signal forsaid differential pressure responsive actuating means, and a meansresponsive to rate of change of temperature in said conduit forproviding a second variable continuous pressure signal proportionatethereto for said differential pressure responsive actuating means.

3. An automatic temperature control system for an enclosure fed from afluid pressure source by a conduit havvso ing-acooling meansttherein, aby-pass'channel for passing fluids around, said cooling means, andra:valve torreontrolling-the llowof fluid through. said by-pass channel;comprising a positional servomechanism for 'operating said valve,`differentialv pressure signal` responsive actuating means responsive toa pluralityl of variablezcontinuous pressure .fsignalstfor controlling;theL operationzof said. positional servomechanism, means responsive toVthe temperature in-` said enclosure for providing a first pressuresignal to` said differential pressure responsive means, and meansresponsive to rate of change of temperature of the iluidin said conduitdownstream of saidby-pass channeland `said cooling `means fforproviding. a second `variable t continuous pressuresignal proportonate.thereto Ato `said differential pressure `responsive means:l

. 4. An automatici temperaturecontrolsystem for.; an enclosure fed froma fluid pressure source .by asconduit having acooling means therein, aby-pass channel for passing lluid around said cooling means, and a valvefor controlling the flow of fluid through said by-pass channel,comprising a pressure responsive control means for said valve responsiveto a control pressure, differential actuating means responsive tovariable continuous signals proportionate to the temperature in saidenclosure and to the rate of change of temperature of the fluid in saidconduit for regulating said control pressure.

5. An automatic temperature control system for an enclosure fed from afluid pressure source by a conduit having a cooling means therein, aby-pass channel for passing fluid around said cooling means, and a valvefor controlling the flow of fluid through said by-pass channel,comprising a pressure responsive actuating means `for said valveresponsive to a control pressure, differen- `differential pressureresponsive means, and means responsive to the rate of change oftemperature of the fluid in said conduit for providing a second variablecontinuous pressure signal proportionate thereto for said differentialpressure responsive means.

6. An automatic temperature control system for an enclosure fed from afluid pressure source by a conduit having a cooling means therein, aby-pass channel for passing fluid around said cooling means, and a valvefor controlling the liow of fluid through said by-pass channel,comprising a pressure responsive actuating means for said valveresponsive to a control pressure, differential pressure responsive meansresponsive to a plurality of variable continuous pressures forregulating said control pressure, means responsive to the temperature insaid enclosure for providing a first pressure signal for saiddifferential pressure responsive means, and means responsive to the rateof change of tempelature of the fluid in said conduit downstream of saidby-pass channel and said cooling unit for providing a second variablecontinuous pressure signal proportionate thereto for said differentialpressure responsive means.

7. An automatic temperature control system for an enclosure fed from afluid pressure source by a conduit having a cooling means therein, aby-pass channel for passing fluid around said cooling means, and a valvefor controlling the flow of fluid through said by-pass channel,comprising a pressure responsive actuating means for said valveresponsive to a first control pressure, differential pressure responsivemeans having a diaphragm oppositely responsive to two different variablecontinuous control pressures for regulating said rst control pressure,means responsive to the temperature in said enclosure for prowding oneof said different control pressures, and means responsive to the rate ofchange of temperature of the fluid in said conduit for providing theother of said two different variable continuous control pressuresproportionate thereto.

8. An automatic temperature control system for an enclosure fed from auid pressure source by a conduit having a cooling means therein, aby-pass channel for passing fluid around said cooling means, and a valvefor controlling the flow of ud through said by-pass channel,` comprisinga pressure responsive actuating means for said valve responsive to a rstcontrol pressure, differential pressure responsive means having adiaphragm oppositely responsive to two diiierent variable continuouscontrol pressures for regulating said iirst control pressure, meansresponsive to the temperature in said enclosure for providing one ofsaid different control pressures, and means responsive to the rate ofchange of temperature of the iiuid in said conduit downstream of saidby-pass channel and said cooling means for providing the other of saidtwo dierent variable continuous control pressures proportionate thereto.

, UNITED STATES PATENTS Peters et al Feb. 12, 1907 Johnson May 6, 1947Sparrow June 28, 1949 Srnith Aug. 2, 1949 Lehane et al Nov. 13; 1951Rusler June 2, 1953 lFOREIGN PATENTS France "Oct. 7, 1953 France July13, 1955 Great Britain Oct. 17,1956

